1. Field of the Invention
This invention relates to a crawler belt drive apparatus for use on crawler type vehicles, particularly suitable for use on construction machines which are equipped with endless crawler belts, for example, as hydraulic power shovels, hydraulic cranes and so forth.
2. Description of the Prior Art
Crawler type vehicles such as hydraulic power shovels and hydraulic cranes are normally equipped with a crawler type drive apparatus which suits for running on rough terrains of construction sites.
Drive apparatus for crawler type vehicles of this sort usually include a drive motor which is mounted on one longitudinal end of a vehicle frame, a power transmission mechanism which is coupled with an output shaft of the drive motor to transmit its rotation at a reduced speed, drive sprockets provided at one end of the vehicle frame on the side of the power transmission mechanism, idler wheels provided at the other longitudinal end of the vehicle frame, and crawler belts each wrapped between a drive sprocket and an idler wheel and constituted by a large number of track links which are connected into an endless form.
More specifically, each crawler belt is provided with a large number of track links in a couple of laterally spaced rows, cylindrical bushes provided between the laterally spaced rows of track links, and a large number of connecting pins fitted in the respective bushes and connecting the track links and the rows of track links to each other. Upon starting the drive motor which is coupled with the drive sprocket, the bushes of the crawler belt are successively meshed with the drive sprocket and the crawler belt is put in a crawling motion around the drive sprocket to put the vehicle in travel.
In this connection, as well known in the art, there has been a problem that large noises (meshing sounds or striking noises) are generated by the drive sprocket and bushes which hit against each other continuously or repeatedly as the bushes of the crawler belt are successively brought into meshing engagement with the drive sprocket.
In order to reduce or suppress such noises (meshing or striking noises) or vibrations of the crawler belt and drive sprocket, various attempts have thus far been made, for example, as described in Japanese Laid-Open Utility Model Applications 55-119281 and 61-183273 which use a rubber or similar buffer material for this purpose.
In the case of the above Japanese Laid-Open Utility Model Application 55-119281, the crawler belt is provided with rotatable buffer members of cylindrical shape between laterally spaced rows of endlessly connected track links alternately with connecting members, in such a way that, as the crawler belt is driven to turn around, the buffer members are brought into abutting engagement with the drive sprocket prior to the connecting members to reduce their striking noises.
On the other hand, in the case of the above Japanese Laid-Open Utility Model Application 61-183273, a plural number of buffer members with resilient pads of rubber or the like are provided in the proximity of sprocket teeth and circularly in the circumferential direction, so that they are abutted against upper and lower edges of the track links of the crawler belt at the time the connecting members are meshed with the drive sprocket, thereby to reduce the meshing noises or vibrations as generated by the meshing engagement with the drive sprocket of the connecting members of the track links.
However, above-described prior art arrangements which use either cylindrical buffer members for a large number of track links of the crawler belt or a plural number of buffer members in positions in the vicinity of sprocket teeth all around in the circumferential direction of the drive sprocket, still have a drawback that the provision of buffer members inevitably entails a substantial increase in cost due to increases in the number of parts and in the number of steps in assembling processes. Besides, the buffer members of rubber or similar material are susceptible to abrasive wear within a relatively short period of time and, therefore, are incapable of maintaining their effects over a long period of time in suppressing meshing noises or vibrations of the crawler belt.